1. Technical Field of the Invention
The invention relates generally to communication systems; and, more particularly, it relates to communication systems operating using cyclic redundancy check (CRC) and, sometimes, at least one redundant transmission therein, to perform error detection and correction.
2. Description of Related Art
Data communication systems have been under continual development for many years. One such type of communication system that has been of significant interest lately is a communication system that employs iterative error correction codes (ECCs) that operate in accordance with forward error correction (FEC). There are a variety of types of ECCs that may be employed in accordance with various communication systems (e.g., that seek to transmit information from one end of a communication link to another). Communications systems with iterative ECCs are often able to achieve lower bit error rates (BER) (or block error rate (BLER) in the context of block codes) than alternative codes for a given signal to noise ratio (SNR).
A continual and primary directive in this area of development has been to try continually to lower the SNR required to achieve a given BER (or BLER) within a communication system. The ideal goal has been to try to reach Shannon's limit in a communication channel Generally, Shannon's limit may be viewed as being the data rate to be used in a communication channel having a particular SNR that achieves error free transmission through the communication channel. In other words, the Shannon limit is the theoretical bound for channel capacity for a given modulation and code rate.
Generally speaking, within the context of communication systems that employ ECCs, there is a first communication device at one end of a communication channel with encoder capability and second communication device at the other end of the communication channel with decoder capability. In many instances, one or both of these two communication devices includes encoder and decoder capability (e.g., within a bi-directional communication system). ECCs can be applied in a variety of additional applications as well, including those that employ some form of data storage (e.g., hard disk drive (HDD) applications and other memory storage devices) in which data is encoded before writing to the storage media, and then the data is decoded after being read/retrieved from the storage media.
While there has been significant and ongoing development in the context of communication systems for some time, there nonetheless continues to be great effort directed to increasing the amount of information that may be transmitted through a communication channel (e.g., from a first communication device location at one end of the communication channel to a second communication device located at the other end of the communication channel) with lower error rates. There is a seemingly continual desire to transmit more and more information via a communication channel with lower and lower error rates. In spite of this, the prior art still does not provide adequate means by which this may be effectuated, and there seems to be a virtually limitless bound in the desire to transmit ever more information with ever lower error rates.